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maxon motor control:Focus on a product line

ESCON:A close lookat some details

2014 maxon motor ag, V1.01

Minimum speed of sensorless control

Any sensorless control requires a minimum speed to evaluatethe motor speed properly based on the Back-EMF signals.

The minimum speed has to be configured in ESCON Studio.

The motor accelerates to theconfigured minimum speed,if the ESCON EC-S is enabledand a set value > 50% of theminimum speed is applied.

ESCON EC-S: Minimum speed

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Minimum speed in practice

Acceleration phase: Set Value < 50% of configured min. speed:

=> Speed = 0 rpm

Set value equals 50 100% of configured min. speed:=> Speed = configured min. speed

Set value > Min. speed:=> Speed = set value

Deceleration phase:Changeover points are linked to 25%of configured min. speed.

ESCON EC-S: Minimum speed

Estimation of the "Minimum speed"

Rule of thumb:Minimum Speed = (Supply Voltage * Speed constant) / 7

Example:24V supply, EC45-flat 30W (#200189)Minimum speed = (24V * 374 rpm/V) / 7 = approx. 1200 rpm

Keep in mind:It is just a rule of thumb!The actual minimum speed has to be checked by manual testsand can even 20-50% below the "calculated" result depending onsome influecing factors.

ESCON EC-S: Minimum speed

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Influencing factors of the minimum speed

Supply voltage Choose the lowest supply voltage, that fulfills the

maximum speed requirements of the application.(12V supply is better than 24V and 24V is better than 48V)

LR of the motor, i.e. inductance and resistance of the windings Prefer windings with a low inductance and resistance.

(Take the minimum required inductance into account:Check chapter "Motor chokes" of EC-S Hardware reference).

Control parameters Start tests and tuning in "Speed Control (Open Loop)" mode

to evaluate the lowest minimum speed.(The required minimum speed of "Closed Loop Control" might be higher.)

ESCON EC-S: Minimum speed

If the automatic tuning does not work properly:

Make sure, that all motor parameters are configured properly!

Configure a minimum speed!(according to the given rule of thumb)

Start tuning with "Speed Controller (Open Loop)"and try to manually tune this configuration first of all.

Check Knowledge Document "ESCON Module 50/4 EC-S: Settings"(DOC ID: 400917) for good hints about parameter optimization.

Adapt "Expert" parameter "Commutation Phase Adjustment"in case of high-inductance motors.

ESCON EC-S: Manual Tuning (Overview)

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ESCON EC-S: Manual Tuning

Click"Show parameters"

Modify"Startup Current","Alignment Time","Sync. Startup "according to thehints given in theKnowledge Document(DOC ID 400917).

Mark"Manual dimensioning"

Some hints, if the motor already shows problems at startup:(see also Knowledge Document "ESCON Module 50/4 EC-S: Settings)

Check, if "Minimum speed" is configured.Typically a good starting point is the"Min. speed = 1/7 of max. speed" rule of thumb.It is even possible to decrease this value in 10% increments until thestartup phase is not "smooth" anymore. Increase the "Minimum speed"then in 20% increments until the startup behaviour is fine again.

"Startup Current"has to be high enough to overcome the breakaway torque.Set startup current to the motor's nominal current and increase thevalue in 20% increments, if the torque is too low to start the movementof the motor. If the starting jerk is too high, decrease the value.

ESCON EC-S: Optimization of Startup

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Some hints, if the motor already shows problems at startup:(see also Knowledge Document "ESCON Module 50/4 EC-S: Settings)

"Alignment Time"is the time in which the motor moves to the rotor start position andstabilizes there before the actual start of movement.Typical values are in the range of 200 1000 ms. Large inertia or lowfriction require a longer "Alignment Time".

"Synchronous Startup Acceleration"depends on the dynamics, load and inertia of the motor.Typically start with a value of 2000 Hz/s for standard or no loadconditions. Try 500 Hz/s in case of a high inertia.If the motor stalls during acceleration or overshoots strongly, decreasethe value in 20% increments. If decreasing does not solve the problem,try to increase the value.

ESCON EC-S: Optimization of Startup

If a motor with a high winding inductance and resistance is in use,

the power supply voltage should be reduced as far as possibletaking acount of the required maximum speed.

the "Expert" parameter "Commutation Phase Adjustment"has to be reduced. The default value is in the range of 20 - 30 anddefines the measuring point of the Back-EMF. If a high inductancemotor is in use, this value can even be reduced to a minimum of 15.

This value can just be accessed,if the User Level is set to "Expert".This has to be done by"File -> Options -> Advanced".

ESCON EC-S: Optimization for high-inductance

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ESCON EC-S: Parameters for sensorless control

Please take profit of the Service & Support Deskand put your request and all your information into an issue:

ESCON *.edc data file !!!! Motor in use (part number)? ESCON product type and part number? Motherboard (or additional chokes) in use? Supply voltage(s) in use (or available, e.g. 12V, 24V, 48V)? Type of application (or short description) Required speed range by the application: Min. and max. speed?

We are pleased to share your experienceand help you to get one step ahead!

ESCON EC-S: Just Ask!